1. Field
The application relates in general to a digital audio/video (AV) capture device and a method thereof, and more particularly to a digital AV capture device and a method thereof, capable of outputting an uncompressed video streaming and a compressed video streaming.
2. Description of Background
Current USB video device class (UVC) audio/video products can be used in Windows XP SP2 and later operating systems or Vista system in a plug-and-play manner without installing any driver. Examples of the UVC AV products include digital webcam, digital camera, analog image converter, TV stick and etc. Webcam, which is one of earliest AV products that support UVC protocol, is widely used and has a large demand in the market.
As the built-in digital webcam has become a standard equipment of a notebook computer, more application of the built-in digital webcam are developed. For example, notebook or personal computer with a built-in digital webcam can be used in digital home or video conference. For this kind of application, video streaming is indispensable. Let video conference be taken for example. Normally, the video streaming has two formats: compressed signal format (such as MPEG) for transmission on the network, and uncompressed signal format (such as YUV format) for playing at local terminal.
FIG. 1 shows a conference frame displayed on a display unit (such as the screen of a notebook or a personal computer) during video conference. As in FIG. 1, during video conference, both a local terminal frame 110 and a remote terminal frame 120 are shown on the display unit. The local terminal frame 110 is a uncompressed video streaming outputted from the built-in digital webcam and played on the display unit of the local terminal computer. The remote terminal frame 120 is a compressed signal outputted from the remote terminal, de-compressed by the local terminal computer and played on the display unit of the local terminal computer.
The conventional digital webcam is disadvantaged by supporting one video format transmission only. For example, all the video streamings outputted from the conventional digital webcam are uncompressed. Therefore, during video conference, the local terminal computer performs compression/decompression, such as, compressing the uncompressed video streaming outputted from the digital webcam and transmitting to the remote terminal computer through a network, and decompressing and playing the compressed signal transmitted from the remote terminal computer. However, the above operation will make the local computer overloaded with compression/decompression.
Thus, example of the invention provide new digital AV capture configuration. The conventional configuration which supports only one flow of UVC real-time isochronous transfer is improved to be capable of supporting two flows of isochronous transfer (that is, capable of transmitting both a compressed video streaming and an uncompressed video stream) by one USB digital AV capture element only (such as only one USB digital webcam). The local terminal computer concurrently receives the video streaming in two formats, so the load of performing compression and decompression by the local terminal computer is reduced.
Moreover, the new USB digital AV capture configuration according to examples of the invention automatically adds a UVC compliant payload header to the video streaming, hence making the implementation in video conference or digital home easier.